looking for recommendation for 50 to 60mm carbon rims
You'll be wanting the Orient Express thread, where people will tell you to get Light Bicycle, unless you're very short of cash in which case take your chances with Aliexpress. I like the look of their RR56C02, and apparently it has reasonable aeros.
What is the smallest tire you would run on a 23mm inner width rim?
I'd be prepared to try a nominal 23 because it would probably come up to 26mm+, what I'm actually using on a 23mm 29er rim on the back of my 464 is a 25C GP4000, which comes up as 30mm.
You'll be wanting the Orient Express thread, where people will tell you to get Light Bicycle, unless you're very short of cash in which case take your chances with Aliexpress. I like the look of their RR56C02, and apparently it has reasonable aeros.